1. Field of the Invention
The present invention relates to a bit selection circuit that selects arbitrary continuous 2n−1 bits from among 2n bits.
2. Description of the Related Art
A circuit that selects arbitrary continuous 2n−1 bits from among 2n bits is used in, for example, image processing or processing for communication.
For example, in the image processing, when a part of an image region is extracted, a processing to select arbitrary continuous 2n−1 pixels from among 2n continuous pixels is performed. In order to implement hardware for executing this processing, it is necessary to arrange circuits for selecting arbitrary continuous 2n−1 bits from among 2n bits to correspond to the number of pixels. As the number of circuits increases, the scale of the entire bit selection circuit increases. Accordingly, there is a need for a technique that can implement a circuit of a smaller scale.
As a specific example, a technique is known in which barrel shifter is used in order to extract a macro block of 8×8 pixels having information about luminance or color difference from a block of 16×16 pixels defined by the MPEG (Motion Picture Experts Group) standard in a circuit for motion detection (for example, see JP-A-10-164596).
In JP-A-10-164596, by a combination of a register (REG) for accumulating data from a memory in a word (8 bits) unit and a barrel shifter, a circuit is implemented which extracts an image block (macro block) of a smaller range from an image block of a larger scale, while shifting a search range, and inputs the extracted image block to a subsequent-stage pipeline processing unit as the arrangement of continuous bits, thereby extracting a macro block.